In servicing, repairing, or carrying out maintenance on aircraft, it is often necessary to determine the type or class of aluminum alloy of an aircraft component, among a plurality of possible different typical aluminum alloys that are used in the structure of an aircraft. This is especially true if documentation regarding repair materials that are to be used does not exist or is not available. In this situation, a complete chemical analysis of the aluminum alloy material would give a clear and precise answer regarding the alloy composition, but such a complete chemical analysis is expensive, complicated, and time consuming and thus not suitable to be used each time the alloy type or class must be determined. Moreover, it is generally sufficient to determine only the general alloy type or class of the material, and it is not necessary to determine the precise alloy composition in most cases.
For this purpose, it has become generally known in the art to use a so-called spot method test, but in actual practice such a spot method test has been found to be unsuitable for the following reasons. In order to carry out the spot method test to identify various aluminum material groups, different test solutions are applied onto the metal surface that is to be tested, in a sequence of individual steps. After each step, the person carrying out the test must reach an opinion as to the type of reaction that occurred due to the interaction of the respective test solution and the aluminum material, based on observed color changes and the like, and in response thereto the person must then decide which test solution is to be used in the next step of the test sequence.
The above described spot test method is relatively time consuming and also complicated and cumbersome due to the sequence of steps that must be carried out using three different test solutions. It is a further disadvantage in the known method, that after each step, the person carrying out the test must once again correctly determine and decide which step using which solution should be carried out next. In this context, any incorrect interpretation of the results in any one of the steps will lead to an incorrect test sequence path that will necessarily cause an erroneous overall result of the test. A further disadvantage is that the color changes resulting from each test step are rather difficult to detect and to distinguish or categorize. For example, color designations such as "gray" or "no discoloration" are freely open to a wide degree of personal subjective interpretation when observed on the metal surface. Moreover, the color change or discoloration resulting after some steps is best recognizable if the testing solution is carefully dabbed off using a cloth without disturbing the material surface, while in other cases the drop of testing solution should be allowed to remain on the metal surface while observing the discoloration.
A further substantial disadvantage or defect in the known method is that one of the described branches of the testing sequence or testing program gives provably false results. Namely, it has been determined that plated and unplated sheet alloy materials of the type or class 7XXX do not react the same way when tested using a hydrochloric acid cadmium sulfate solution. Thus, at least for materials of the alloy class 7XXX, the known drop or spot method test is not functional when carried out in the above described manner.